\documentclass[]{article}
\usepackage{amsmath,tkz-linknodes}
\usepackage{tikz} 

%\usepackage[graphics,tightpage,active]{preview}
%\PreviewEnvironment{NodesList}
\newlength{\imagewidth}
\newlength{\imagescale}

\input{common}

\begin{document}
\thispagestyle{empty}
        \begin{NodesList}[margin=2.5cm] 
\begin{align*}
  \alpha [\phi] [\psi \wedge \chi] & = \alpha [\phi] [\psi] \sqcap
  \alpha [\phi] [\chi] \AddNode \\
  & = \alpha [\phi \wedge \psi] \sqcap \alpha [\phi \wedge \chi]
  \AddNode \\
  & = (\alpha [\phi] \sqcap \alpha [\psi]) \sqcap (\alpha [\phi]
  \sqcap \alpha [\chi]) \AddNode \\
  & = \alpha [\phi] \sqcap (\alpha [\psi] \sqcap \alpha [\chi])
  \AddNode \\
  & = \alpha [\phi] \sqcap \alpha [\psi \wedge \chi] \AddNode \\
  & = \alpha [\phi \wedge (\psi \wedge \chi)] \AddNode \\
\end{align*}
 
 \tikzset{LabelStyle/.append style = {\myside}
            ,ArrowStyle/.append style = {draw=\mydraw}
           }

\LinkNodes{Inductive step}
\LinkNodes{Definition}
\LinkNodes{Boolean algebra}
\LinkNodes{Definition}
\LinkNodes{Definition}
   \end{NodesList}
\end{document}